Signature and Long-Term Nimbus are unchanged, as these are more narrative effects.
Nimbus Tilts
The Nimbus Tilt itself is still constructed as normal: You gain Gnosis/2, rounded up, dice to allocate to either providing benefits or penalties to Attributes. Alternatively, you can use these dice to benefit Skills, giving them 8-Again, or penalizing them, eliminating 10-Again - if the penalized Skill has 8- or 9-Again from a mundane source, the Nimbus overrides it, eliminating the effect; from a supernatural source, it provokes a Clash of Wills, using Gnosis + the initiating Mage's highest Arcanum.
Immediate Nimbus
The Immediate Nimbus of a Mage is obvious to Mage Sight, whenever they cast a spell, as the Mage's particular connection to the Supernal becomes more obvious and present. This has no immediate effect, though if a Mage suspects they are being observed with Mage Sight while casting, they can reflexively spend a point of Mana (still restricted to their Gnosis-derived maximum per round) to inflict their Nimbus Tilt on the watcher.
At any time, as an instant action, a Mage may flare their Nimbus, revealing it to the Fallen World and all that may be watching. This costs one point of Mana to do so and lasts for a number of rounds equal to the Mage's Gnosis. This can be extended to last until the end of the scene by reflexively spending a point of Willpower at any time while the Nimbus is active. All individuals who witness the flared Nimbus, and are within Gnosis x 10 yards, are immediately affected by the mage's Nimbus Tilt. If the Mage wishes, they can attempt to control who their Nimbus affects by rolling Wisdom - each success on this roll either allows them to exclude one person, or decrease their effective Gnosis by one for purposes of determining their effective range; if reduced to zero, they can affect only those within arm's reach. An Exceptional Success allows them to exclude as many people as they wish, while a Dramatic Failure likely has considerable drawbacks, as the Mage loses control of their Nimbus.
Sleepers typically cannot resist the Nimbus Tilt(and may suffer a Breaking Point depending on the Tilt), though mages and other supernatural creatures can attempt to do so. Doing so is an opposed roll with the initiating Mage rolling a Power Attribute (which must be of the same category as at least one of the affected Attributes or Skills) + Gnosis, and the defending Mage rolling the same category Resistance Attribute + Gnosis. If the defending Mage wishes, instead of cloaking and shielding themselves in their own Nimbus, they can instead attempt to push back and override the initiating Mage's Nimbus, instead spending a Mana and rolling their appropriate Power Attribute + Gnosis. In this case, whoever is successful inflicts the Beaten Down Tilt on the other for a number of rounds equal to their Gnosis. Additionally, if successful, the defending Mage can flare their Nimbus on their next turn without spending a point of Mana.
Other supernatural entities can resist in a similar manner, exerting their own auras, as appropriate.